The snake that killed two young boys in an apartment above an exotic pet store in Campbellton, N.B., had escaped from its enclosure before, according to a snake expert who is assisting police and has been briefed on the case.

Barely able to keep the anger out of his voice, Bry Loyst, curator of the Indian River Reptile Zoo, told QMI Agency that Monday wasn't the first time the African rock python had made its way into the ventilation system.

"This was an accident waiting to happen," said Loyst, who was en route to Campbellton, about 475 km north of Saint John.

Noah Barthe, 4, and his brother Connor, 6, were found dead around 6:30 a.m. Monday. The RCMP said the boys were at a sleepover with the son of the owner of Reptile Ocean, who lives above the store.

Store owner Jean-Claude Savoie, who told Global News the snake is his pet and wasn't for sale, said he is reeling from the tragedy.

"My body is in shock. I don't know what to think," he told the broadcaster.

"I feel like they're my kids."

Savoie said he found the two boys in the living room and thought they were sleeping. His son was in another room and unharmed.

"I turned the lights on and I (saw) this horrific scene," he said.

Police said they believe the 45-kg snake entered the ventilation system through a vent above its enclosure, which reached nearly to the ceiling of Savoie's apartment. A pipe broke, and the snake fell into the living room where the boys were sleeping on a mattress.

A provincial vet euthanized the snake and a necropsy will be performed, police said.

Loyst said police told him the children had been at a petting zoo until as late as 10 p.m.

He guessed that the snake, after escaping its pen, followed the scent of those animals.

National Geographic describes the African rock python as "one of the world's most vicious." It can grow to six metres — double the length allowed under the province's exotic wildlife regulations unless the owner has a special permit, the department of natural resources said Tuesday.

The penalty, under the Fish and Wildlife Act, is a fine of $50 to $300.

Police wouldn't comment on whether Savoie had the proper permits, saying that is a matter for the province, but police did say they're treating the case as a criminal investigation "even though the suspect is not a human."

Loyst said lax laws are to blame for the tragedy.

He said only about 25 of Canada's approximately 200 zoos and aquariums are accredited facilities, required to meet the safety and animal care standards set out by Canada's Accredited Zoos and Aquariums (CAZA).

The boys' great-uncle, Dave Rose, speaking on behalf of the family at a news conference Tuesday, said Noah and Connor were "typical" kids who "enjoyed life to the fullest."